Television apparatus



` Filed Oct. 21, 1936L 3 SheeLS--Sheekl 1 FIG! INVENTOR Volnej D.Horc{.

ATTORNE I Jan; 21, 1941.

v. D. HURD TELEVISION APPARATUS 3 Sheets-Sheet 2 Filed Oct. 2l, 1936 v.D. HURD 2,229,456 TELEVI S ON APPARATUS Jmzl, 1941.

Filed oct. 21, 19:56 :s sheets-sheet s INVENTOR for ATTORM? Y PatentedJan. 21, 1941 UNITED `,STATES PATENT FFICIE 4 Claims.

The present invention relates to the art of television and in particularto a method and system of `scanning that `has for its purpose theproduction of improved television pictures and moreefcient and cheaperscanning means than at presently used.

The art of picture transmission has been the object of development workfor a .great many years. The methods initially employed areY chiefly vofa mechanical `nature and lmore recently thesemethods .have beengenerallydisregarded as the use of vacuum tube control :means has:become publicized.

The `general Atelevision systems may be separated into two classes,the.so called mechanical method of scanning and the scanning with theuse of a cathode lbeam commonly embodied in the cathode ray tube. Themechanicalscanning system is somewhat misnamed since it .employs'electricalmeans `The ,chief distinctionshowever lbetween the `twosystems is lthat inthe mechanical scanningmethod, ascanning discisemployed `by which alight `-,bearnis made-to travel a certain definitecourse. [In the system `employing the 20 cathode ray tube., :the cathodeAbeam corresponds :to :the light ,beam and this is made .-toscan .theAobject `whose image is to .be tra'nsmittedlby electrical .control ofthe :course :of l.the beam.

The present invention relatesin Yfact .to .both methodsofscanningiandmay beapplied equally to ,eachrmethod to produce theimproved results. 'The Iinvention :similarly applies .to `the .systemused at .the reproducing Tend askmay well`be eX- ;pected sin-ce thereproducing end mustalways be '35 4.related :in synchronism of 4movementwith the movement ofthe Abeam at Athe transmitting end.

The invention also applies with ,particular merit .to a mechanicalscanning system not only `on `account A rif the simple mechanism .which`may 40 lbe incorporated in the mechanical .means to produce the desiredresult, but also .because ,it allows rthe 'mechanical system -toovercome `certain `ob- .J'ectionable features which have previously beenpresent in Systems-of this nature.

With all the development in the art of tele.-

vision which has .taken place since its inception, the art itself `hasup .to the .present time been retarded -in its full .commercialVdevelop- `ment fora number Vof reasons. The cost of the apparatus isVstill too `expensive to allow widespread sale. vInaddition .tothis the.radio channels over which the signals must be transmitted Aare limited.and the ,apparatus itself is still too .imperfect to ,produce ,resultsthat can readily be enjoyed. The .limitation of the channel `over whichthe transmission must bemade is ,caused not only because of the lack ofthe so called broad `band of frequencies available, but also becausetelevision to be transmitted perfectly must be given a very broadchannel frequency `.5

in order to provide proper definition ofthe pictures to `be transmitted,that isv to say, 'the picture frequency isdirectly related to thenecessary band frequency width and with a high enough picture frequencyand line frequency `to l0 `provide a proper picture definition, thechan- .nel band frequency must 4be beyond the limits that ordinarily arepossible to assign.

The present invention `is particularly adaptable to overcome these.diiiiculties and toprovide l5 a clear denition of the ,picture with alower line frequency or with the same line frequency at presentavailable. The present invention is chiefly Vconcerned with overcomingvthese particular diliculties and amongst other things 2O provides inits selection of frames a composite picture which multiplies theclearness of lthe denitionof the picture itself. This will "be'morereadily .understood .from the description given in the specicationbelow. The present inven- 2:3 tion also provides these results ,in asimplemechanism and further furnishes a simple scanning means which inits various features produces a more perfect picture than has beenpossible before.

The present type of invention also contemplates using a particular typeof screen and may also 4employ particular scanning means as describedbelow.

In addition to the above, Ywhere afmechanical 35 means is employed, asfor instance a drum or disc, or even with pure electrical methods, Vthescanning spot may be narrower inthe direction that it moves and wider inthe direction normal to it. Using this type of beam or opening, clear'40 definition of vthe picture will be obtained in a vdirection normaltothe scanning `because of the overlapping effect as will be notedbelow, and in addition to this, clear definition will `be obtained inthe direction of the motion of the beam be- 45 cause of the narrownessof the Yspot which may be employed.

The invention Will be further described -in connection with thedrawings, in which:

Figure 1 illustrates more or `less diagram- 50 matically the scanningsystem preferably employed.

Figure 2 shows the `application of such a system in combination with afeatureof criss-cross scanning.

Figure 3 shows a further modification of the system as set forth inFigure 2.

Figure 4 shows a detail of an element indicated in Figure 3.

Figure 5 shows a further modification of the system indicated in Figure2.

Figure 6 shows a fragmentary view of the de tails of the screen.

Figure 7 shows a cross sectional View of the element shown in Figure 6.

Figure 8 shows a still further modification of a selective line scanningdrum, and

Figure 9 lshows an auxiliary view taken on a section 9-9 of Figure 2.

In the arrangement shown in Figure 1, the system may be considered asthe receiving end in which the light tube I responds to the currentimpulses transmitted by the wires 2 2 to produce a light image of anintensity corresponding to that at the same instant at the transmittingend. The light may be transmitted through a concentrated lens 3 andpassed through the slots 4, 4, 4, etc., in the disc 5 and reflected fromthe mirror 6 to the screen 'I. The spot image in the screen may berectangular with the narrow dimensions in the direction that the spot ismoved. In the .arrangement shown in Figure l, the disc 5 is the scanningdisc and is driven by means of the shaft 8 through the motor 9 which isrun in synchronism with vthe transmitter system. Carried to the shaft ofthe motor 9 at the opposite end is a gear III which operates a secondgear I I in a reduction system which in turn drives the mechanism whichwill be described presently.

The mirror 6 is pivoted in supporting bearings I2 and I3 so that it isfree to be moved slightly about a vertical angle. Carried by the mirrorframe is the arm I4 which is tensioned to the cabinet I5 by means of thespring IS. The end of the arm I4 carries a dependent V Il bearing upon acam I8 which is mounted on the shaft I9 also carrying the gear 2l). Thegear 2li meshes with the' worm 2| which is slidably mounted upon theshaft 22 by means of the ribbing 23 so that the worm may be placed bymoving the handle 24 carrying the support 25 in any position along theshaft. In this vway the position of the vearn under the dependent V Ilmay be adjusted to the desired point and thus the mirror 6 may have itsinclination changed to produce the results desired. The shaft 22 isdriven through the gears 26 and 21, the gear 2l being mounted on a'shaft2B which is driven by the gear II mentioned above.

In the operation of the system each hole in the scanning disc 4, 4,causes the beam of light to sweep across the screen, successive holesbeing so positioned that different lines are scanned with each holeuntil all of the lines as indicated v in the screening 'I may bescanned. This may be accomplished by a single revolution of the screendisc 5, or it may be accomplished in part of a revolution dependent ofcourseupcn the arrangement of holes and the speed of scanning.

If the scanning drum shown in Figure 8 is used, the scanning of a singleframe may be accomplished by, what I call, an X scanning method. In thiscase the scanning slot Sil'furnishes the first line of scanning, BI, thesecond, 82 the third, 83 the fourth and so on, the position of thescanning slots forming the shape of a letter.

In this method of scanning the whole picture is filled in over itsentire surface morevor less uniformly, that is to say, the picture doesnot grow from the top down or from the bottom up,

but the successive lines scanned are so distributed over the wholepicture, that the whole picture takes a gradual form. This method has atendency of eliminating the flicker that is commonly present in othermethods of scanning.

In order to produce the picture that is transmitted at the sending end,it is of course necessary to repeat the same pattern that the scanningdisc at the transmitting end is going through. This may obviously bedone by having the motor 9 operate in exact synchronism with thescanning mechanism at the transmitting end and having a disc 5 exactlythe same as the transmitting disc at the transmitting end. In additionto this mechanism however in the present system, the transmitting endmust have a corresponding mirror system, the inclination of which isgoverned in accordance with a device like that shown in the presentgure.

If the mirror in the present case were omitted, then eachJ line that wasscanned at the trans-- mitting end of each linethat was produced at thereceiving end would correspond and would repeat itself in one scanningcycle. Therefore if a picture were a 60 line picture, the picture wouldrepeat itself in exactly the same position for each 60th line.

The present mechanism produces a different scanning arrangement and hasfor .one of its chief objects the reproduction of the picture to betransmittedl by successive different scannings. If the picture is tobescanned with 60 lines for one frame, then the present arrangementscans the next frame, not in the same 6) lines asin the original framebut with 60 lines that are somewhat displaced. The third frame maysimilarly be'slightly displaced from the second frame so that notwo'successive frames will scan the same lines.

In the mechanism therefore in the present application, it will be notedthat the cam I8 moves the arm I4 very slightly in a complete revolutionwhich is so adjusted to extend over a considerable number of frames. Theline 30 scanned in the mechanism as shown, when repeated on the nextscanning will be slightly displaced,isince at that time the angle ofinclination of the mirror 6 will be such `as to throw the line eitherupwards slightlyor downwards as the case may be. The mirror maysubstantially retain its position over a complete frame and then at thenext frame may take up a second position in which the lines 30 and allof the other lines become slightly displaced. This overlapping of thelines of the picture bring out the denition of the elements between thelines and even with a frame of fewer lines provides a more clearlydefinite picture than where the lines are repeated in exactly the sameposition. Progression of theinclination of the mirror may be continuousin which case the successive lines in the frame will be varied. Thechoice of the method to be employed can be wholly accomplished by theproper selection and design of the cam I8. After one cycle of the cam IBthe frames again repeat themselves in the same position, butthis'interval is large as compared to the interval between successiveframes and may even be of Vanother order of magnitude; that is to say,each 10th or 20th frame may repeat itself or if desired of coursetherepetition may be cut down so that each 5th frame may repeat itself.

In adjusting the receiving system to correspond to the sending system,the synchronism of the motor 9 is of course established'with that'of themotor at the transmittingend. Ifthepelements are in exact synchronism`Ithepicture be produced clearly. If however, the "mirror'6 has :nottheproper angle, the picture maybe `somesingle line. This method ofscanning Vit will be observed is practically equivalent to theproduction of a picture `of lines which is theproduct of a number oflines in `the'frame andthe number of successive frames untilthe iframehas exactly repeated itself. In 'this'theapplicant has further foundthat there is no limit to the number 'of different elements which may beused before a frame is Iexactly reproduced, the increased improvementhowever being noticeable with displacements of 5 and 10 frames beforereproduction occurs. It is the applicants estimate that probably themaximum improvement can be obtained with some displacement rangingbetween 10 and 20 frames.

In this method of scanning an ordinary scanning disc is shown. Thesystem may however incorporate a drum in which the light source isobtained in somewhat a different manner. In most so called mechanicalmethods of scanning there is an ineil'cient utility of light source,either a whole plate is lighted to obtain a tiny light spot or thescanning ls obtained by movement of a lens or mirror from a small lampsource.

In the present system the applicant may use a substantially powerfullight source which is iixed in such a way that the association ofrelative positions of the mask and the scanning drum are such as toproduce the desired movement of the scanning beam. Instead of using afutile pin-point of light, a spot source 3l giving plenty of intenselight is usable. 'Ihe mask 32 may be positioned in front of the lightsource and provided with an opening 33 of the desired size. This may be1A," to 1A" in diameter dependent upon the size 34 of the holes in thedrums and the position of the other related parts of the system. Asindicated perhaps more clearly in Figure 4, the opening 34 in the drum35 must be such` as to sweep the beam, 36 across the mirror 3l andproduce a corresponding line across the screen 38. 'I'he drum 35 may berotated in the same manner as the scanning disc 5 of Figure 1 and thevarying of the position of the line across the screen 38 may beaccomplished by moving the mirror 3l in a manner similar to that of themirror 6 in Figure 1. The light from the mirror 31 is concentrated bymeans of a lens 39 which focusses on the screen 38. The type of scanningindicated in Figure 3 is so called spiral scanning since the holes 34,34, etc. on the disc 35 are arranged in a helical spiral in which eachopening in the drum corresponds to one line, that is, scanned across thescreen 38. The holes 34, 34 on the scanning drum 35 are preferablyspaced apart substantially the width of the holes themselves. It shouldbe noted in this respect that as one hole leaves the eld of the lightbeam, for instance the opening 33 in the mask 32, that the next holeapproaches the beam so that in this `wayuninterrupted'successivescanning `of successive lines isobta-ind.`

In place rolf thi'ssystem, `the systemshown in the mechanism `in FigureZmay be used. Inthis, the displacementof the frames may also beVaccompanied-by a criss-'cross scanning of the ,picture. In this figurera scanning disc 40 maybe used in which the holes 4l are placed in aspiral arrangement similar to that indicated in Figure 1. There may beas indicated in'this i'lgure'two sources of light 42 and 45, the source42 being placed at a point where the holes 4l travel horizontally acrossit. In frontof the disc,- there may be positioned aA reilecting prism43, which together withthe source and thehole in the disc Vproduces theline 44 as indicated in the gure.

The vertical lines are produced by means of the source45 which ispositioned ata place where the holes in the disc pass before the source.in a general .vertical direction. In front of the discthere ispositioned the prism 46 which elements vproduce the vertical line '41..The displacements 'of `the vertical lines in successive frames inaccordance with the device indicated in Figure 1 may be accomplished bycontrol of the prism 46, and similarly the displacement of thehorizontal lines may be controlled by movement of the prism 43. Theprism 46 is supported for rotary motion by means of the shaft 80journaled in bearings 8|, 8 I. The displacement of the lines isob-tained by means of the mechanism 82' operated by the handle 24 whichis the same as that shown in Figure 1. This mechanism is driven by thegear 83 which operates on an extension of the shaft 49 and drives thegear 84. The same type of mechanism is used on the prism 43. Preferably,first a vertical frame and then a horizontal frame are scanned, or viceversa and this may be accomplished as schematically indicated by someswitching system associated and synchronized with the control of thescanning disc. In this case the mo-tor 48 driving the scanning disc 40may also drive on the shaft 49 the gear system 50 and 5| which rotatesthe shaft 52 carrying the cam 53 controlling the operation of thecontacts 54, 55 on one side of the cam and 56, 51 on the other side ofthe cam. As the circuit to one light is closed, so the circuit to theother light is open so that successive first one source is connected andthen the other separate circuits may be provided but as indicated in thei'lgure, a single circuit 58 is provided with which the two lightsources are in parallel, the switch mechanism being located in eachparallel flange. In place of the 90 criss-cross scanning as indicated inFigure 2, a lesser disc may be used as suggested in Figure 5, Where thetwo light sources 59 and 60 are indicated at positions with the aXis 6Iof the scanning disc 62 at approximately 60, the screen 63 being scannedin the manner as indicated by the lines thereon. In order to obtain ascreening with the best possible visible effect, a screen may beemployed as indicated in Figures 6 and 7. In these figures the screen 64is provided with a great number of convexed or concaved reecting mirrors65, the mirrors 65 being preferably smaller than the light source so asto produce reflections in all directions. The screen 64 is preferably ofsome highly reflective material, such as silver or the like, and thearrangement of a great number of small reflecting mirrors on its surfaceso reflecting the light falling upon it that the image may be viewedfrom the side as well as positions directly in front of it. A screen ofthis type also provides eiiicient light reflection and makes it possibleto see the image even with a comparatively poor light source.

Having now described my invention, I claim: 1. In a television system,means for scanning 4 comprising a scanning disc havingtwo sources oflight, one sourceof light positioned with relation to the scanning discfor producing" one group of parallel lines of scanning, the secondsource of light being positioned to produce a'second group of parallellines of scanning, each of said groups being positioned relative to theother, and means positioned in front of said scanning disc for controlling the displacement of the scanning from a distance less than thewidth of the scanning line.

2'. In a television'system, means for reconstituting a picture of anobject scanned by similar means at the transmitting end, comprisingmeans for producing said pictureby successive line developmentsconstituting a frame, means for cyclically varying the position of thelines of the frame by a space less than the Width between successivelines and means provided only at the picture producing station formanually ad justing, the phase of the-cycle independent of said lpictureproducing means.

3. In a-television system, a rpicture producing means comprising meansfor producing a picture by successive line developments comprising thepicture frame, means for cyclically advancing the line position in eachframe by a comparatively small value and means for advancing orretarding the phase of said cyclic variation to bring the linedeiinition of the picture in clear outline independent of said pictureproducing means.

4. In a television system, a picture producing means comprising ascanning disc and a light source, means reecting the beam from thescanning disc to the producing screen, means for producing adisplacement of the beam in successive picture frames a small amount incyclic progression and means manually operative to adjust the phase ofthe cyclic progression for sharpening the lines of the produced pictureindependent o said picture producing means. l

VOLNEY D. HURD.

